[c-nsp] FabricPath & PIM-SM Interoperation

[Tim Stevenson]

At 08:43 AM 9/17/2013  Tuesday, Yuri Bank noted:
>Hi Tim,
>
>Thanks for your response.
>
>I should have phrased my question differently. I'm not suggesting 
>that FP IS-IS actually interacts with PIM-SM directly.
>
>My question is:  Will the FP device, which is running PIM-SM on some 
>SVI, send PIM Register/Join messages for learned multicast 
>sources/receivers in the FP domain?

Yes, absolutely.



>Imagine the following scenario.
>
>You have DeviceA and DeviceB.
>
>DeviceA is a FP switch, with an entire FP domain behind it.
>DeviceB is a legacy multilayer switch, or router, with many other L3 
>devices behind it.
>
>DeviceA has an FP-VLAN with a PIM-SM enabled SVI in it.
>DeviceB simply has a layer3 interface (in the above vlan) with PIM-SM enabled.
>
>Now the RP, sits somewhere behind DeviceB. Obviously, if there is a 
>host somewhere in the FP network that starts sending multicast 
>traffic, DeviceA will have to send out a PIM-Register message in 
>order for the RP to learn of the source(otherwise, only hosts in the 
>FP network would be able to listen to that traffic).


Yes, the FP switch with the SVI will attract the multicast traffic 
(learned as an mrouter) and once that traffic hits the SVI all the 
usual first hop router mechanisms for L3 multicast kick in.


>Likewise, if there is a multicast receiver in FP network, a PIM-Join 
>message would need to make its way to the RP.


IGMP snooping intercepts the join at the edge switch to track state 
on the edge port. That join will be flooded on the mrouter ports (and 
also handed over to FP ISIS to advertise the edge switch's interest 
in that group in FP via GM-LSPs.) Once the join hits the SVI all the 
usual last hop router mechansims kick in.

Tim


>Does this make sense? Again, I greatly appreciate your response.
>
>-Yuri Bank
>
>
>
>On Tue, Sep 17, 2013 at 9:46 AM, Tim Stevenson 
><<mailto:tstevens at cisco.com>tstevens at cisco.com> wrote:
>Hi Yuri, please see inline below:
>
>At 03:27 AM 9/17/2013  Tuesday, Yuri Bank clamored:
>
>Hello fellow networking enthusiasts,
>
>I have a few specific questions concerning this:
>
>1. *Will a N7k/N5k translate GM-LSPs into PIM-Join messages, on a boundary
>link that has a remote peer running PIM-SM?
>
>
>
>No. FP ISIS GM-LSPs are an L2 concept here, they basically track 
>group membership state at L2 inside the FP core. FP ISIS would not 
>"peer" with a router running PIM-SM; you would typically have an SVI 
>enabled for the FP VLAN, and that would have PIM enabled to integrate to L3.
>
>
>
>2. *Same question as it relates to sources learned, that are within the
>FabricPath domain. Will PIM Register messages be generated, and sent to the
>RP in the PIM-SM domain?
>
>
>
>Not without an SVI/router interface running PIM connected into the FP domain.
>
>
>
>
>3. *Any general information regarding this topic would be greatly
>appreciated, as I could find very little documentation about this.
>
>
>
>Think of FP GM-LSPs as an extension of IGMP snooping. All the L3 
>integration is basically the same in FP and classical Ethernet.
>
>
>Hope that helps,
>Tim
>
>
>
>
>
>Regards,
>
>YuriB
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>
>Tim Stevenson, <mailto:tstevens at cisco.com>tstevens at cisco.com
>Routing & Switching CCIE #5561
>Distinguished Technical Marketing Engineer, Cisco Nexus 7000
>Cisco - <http://www.cisco.com>http://www.cisco.com
>IP Phone: <tel:408-526-6759>408-526-6759
>********************************************************
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Tim Stevenson, tstevens at cisco.com
Routing & Switching CCIE #5561
Distinguished Technical Marketing Engineer, Cisco Nexus 7000
Cisco - http://www.cisco.com
IP Phone: 408-526-6759
********************************************************
The contents of this message may be *Cisco Confidential*
and are intended for the specified recipients only.